What does \"string axis\" mean? What are the phenomena, and how to deal with them?

It’s shaft play; as the name suggests, it refers to the axial movement of the shaft. It’s a design flaw – the axial forces aren’t properly balanced； The pump’s rotor is not at the hydraulic center position ； The dynamic balance of the impeller is not properly done ； An improper bearing arrangement can lead to the inner or outer rings of the bearings moving, resulting in bearing damage. In multi-stage pumps, it is necessary to check whether the balancing device is worn out and whether the balancing pipes are blocked ；

As mentioned above, once the pump starts operating, the inlet side is the low-pressure side while the outlet side is the high-pressure side. At this point, an axial force acts from the high-pressure side to the low-pressure side on the backplate of the impeller, causing the rotor to move toward the low-pressure inlet side. This force is known as the axial force. There are various ways to balance this axial force; for example, balance holes can be created in the impeller, or a balance chamber can be designed behind the impeller’s backplate. The balance holes connect the inlet chamber with the balance chamber. It is also possible to use symmetrically arranged impellers. Multi-stage pumps are equipped with balancing devices such as balance discs, balance hubs, and balance pipes. Double-suction impellers can also be used. Generally, pumps have positioning bearings at the high-pressure end; angular contact ball bearings are installed back-to-back or face-to-face, or thrust discs and thrust bearings are used to prevent the rotor from moving axially due to axial forces. What is the model of your pump? That will help us determine the cause of the issue

Axial play actually refers to axial movement, that is, the inevitable slight movement of the motor’s shaft along its axis during operation. The axis direction is the direction of the axis, while the direction perpendicular to the axis direction is the direction of the cylindrical surface of the axis

Due to unreasonable design, the pump shaft often experiences significant axial movement, which is highly detrimental to the use of mechanical seals. This phenomenon often occurs in multi-stage centrifugal pumps, especially during the startup process when the amount of shaft movement is relatively large.

The motor shaft must not shift at any time; a slight amount of movement has little impact on the motor itself. However, excessive shifting leads to an increase in current, rising motor temperature, increased mechanical stress, and it may also affect other equipment